Semiconductor packages and methods of forming same

ABSTRACT

In an embodiment, a package includes a first package structure including a first die having a first active side and a first back-side, the first active side including a first bond pad and a first insulating layer a second die bonded to the first die, the second die having a second active side and a second back-side, the second active side including a second bond pad and a second insulating layer, the second active side of the second die facing the first active side of the first die, the second insulating layer being bonded to the first insulating layer through dielectric-to-dielectric bonds, and a conductive bonding material bonded to the first bond pad and the second bond pad, the conductive bonding material having a reflow temperature lower than reflow temperatures of the first and second bond pads.

PRIORITY CLAIM AND CROSS-REFERENCE

This application is a continuation of U.S. application Ser. No.15/980,541, filed on May 15, 2018, entitled “Semiconductor Packages andMethods of Forming Same,” which claims the benefit of U.S. ProvisionalApplication No. 62/537,736, filed on Jul. 27, 2017, entitled“Semiconductor Packages and Methods of Forming Same,” which patentapplications are incorporated herein by reference.

BACKGROUND

The semiconductor industry has experienced rapid growth due to ongoingimprovements in the integration density of a variety of electroniccomponents (e.g., transistors, diodes, resistors, capacitors, etc.). Forthe most part, improvement in integration density has resulted fromiterative reduction of minimum feature size, which allows morecomponents to be integrated into a given area. As the demand forshrinking electronic devices has grown, a need for smaller and morecreative packaging techniques of semiconductor dies has emerged. Anexample of such packaging systems is Package-on-Package (PoP)technology. In a PoP device, a top semiconductor package is stacked ontop of a bottom semiconductor package to provide a high level ofintegration and component density. PoP technology generally enablesproduction of semiconductor devices with enhanced functionalities andsmall footprints on a printed circuit board (PCB).

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1 through 3, 4A-4O, and 5 through 14 illustrate cross-sectional ofintermediate steps during a process for forming a package structure inaccordance with some embodiments.

FIGS. 15 through 21 illustrate cross-sectional views of intermediatesteps during a process for forming a package structure in accordancewith some embodiments.

FIGS. 22 through 28 illustrate cross-sectional views of intermediatesteps during a process for forming a package structure in accordancewith some embodiments.

FIGS. 29 through 34 illustrate cross-sectional views of intermediatesteps during a process for forming a package structure in accordancewith some embodiments.

FIGS. 35 through 38 illustrate cross-sectional views of intermediatesteps during a process for forming a package structure in accordancewith some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Embodiments discussed herein may be discussed in a specific context,namely a package structure (e.g., a package on package (PoP) structure)including dies bonded together with a hybrid bonding technique. The diescan be bonded together face-to-face (F2F) or face-to-back (F2B). Forexample, in a F2F bonding configuration the active surfaces (faces) ofthe dies are bonded together, whereas in a F2B bonding configuration, anactive surface of one die is bonded to a back surface of another die. Inaddition, the hybrid bonding between the dies includes adielectric-to-dielectric bonding and a metal bonding. For example, byincluding a solder bonding (instead of, for example, copper to copperbonding), the bonding temperature of the hybrid bonding can be loweredsignificantly.

Further, the teachings of this disclosure are applicable to any packagestructure including one or more semiconductor dies. Other embodimentscontemplate other applications, such as different package types ordifferent configurations that would be readily apparent to a person ofordinary skill in the art upon reading this disclosure. It should benoted that embodiments discussed herein may not necessarily illustrateevery component or feature that may be present in a structure. Forexample, multiples of a component may be omitted from a figure, such aswhen discussion of one of the component may be sufficient to conveyaspects of the embodiment. Further, method embodiments discussed hereinmay be discussed as being performed in a particular order; however,other method embodiments may be performed in any logical order.

FIGS. 1 through 3, 4A-4O, and 5 through 14 illustrate cross-sectional ofintermediate steps during a process for forming a package structure inaccordance with some embodiments.

FIG. 1 illustrates an integrated circuit die 100 at an intermediate stepin processing. The integrated circuit die 100 may be a logic die (e.g.,central processing unit, mobile application processor, ASIC, GPU, FPGA,microcontroller, etc.), a memory die (e.g., dynamic random access memory(DRAM) die, a Wide I/O die, a M-RAM die, a R-RAM die, a NAND die, astatic random access memory (SRAM) die, etc.), a memory cube (e.g. HBM,HMC, etc.), a high data rate transceiver die, a I/O interface die, a IPDdie (e.g. integrated passives device), a power management die (e.g.,power management integrated circuit (PMIC) die), a radio frequency (RF)die, a sensor die, a micro-electro-mechanical-system (MEMS) die, signalprocessing dies (e.g., digital signal processing (DSP) die), a front-enddie (e.g., analog front-end (AFE) dies), a monolithic 3D heterogeneouschiplet stacking die, the like, or a combination thereof.

Before the intermediate step illustrate in FIG. 1, the integratedcircuit die 100 may be processed according to applicable manufacturingprocesses to form integrated circuits in the integrated circuit die 100.For example, the integrated circuit die 100 includes a semiconductorsubstrate 102, such as silicon, doped or undoped, or an active layer ofa semiconductor-on-insulator (SOI) substrate. The semiconductorsubstrate 102 may include other semiconductor material, such asgermanium; a compound semiconductor including silicon carbide, galliumarsenic, gallium phosphide, indium phosphide, indium arsenide, and/orindium antimonide; an alloy semiconductor including SiGe, GaAsP, AlInAs,AlGaAs, GaInAs, GaInP, and/or GaInAsP; or combinations thereof. Othersubstrates, such as multi-layered or gradient substrates, may also beused. Devices, such as transistors, diodes, capacitors, resistors, etc.,may be formed in and/or on the semiconductor substrate 102 and may beinterconnected by interconnect structures formed by, for example,metallization patterns in one or more dielectric layers on thesemiconductor substrate 102 to form an integrated circuit. Theinterconnect structures are formed using damascene and/or dual-damasceneprocess, in some embodiments.

The integrated circuit die 100 further include pads 104, such as copperpads or aluminum pads, or a combination thereof to which externalconnections are made. In some embodiments, these pads 104 may be used ina hybrid bonding configuration to bond the integrated circuit die 100 toanother die or structure. The pads 104 are on what may be referred to asan active side of the integrated circuit die 100. Insulating layers arealso on the active side of the integrated circuit die 100. In someembodiments, the insulating layers are formed of a polymer, which may bea photo-sensitive material such as polybenzoxazole (PBO), polyimide,benzocyclobutene (BCB), or the like. In other embodiments, theinsulating layers are formed of a nitride such as silicon nitride; anoxide such as silicon oxide, phosphosilicate glass (PSG), borosilicateglass (BSG), boron-doped phosphosilicate glass (BPSG); a combinationthereof or the like. The insulating layers may be formed by spincoating, lamination, chemical vapor deposition (CVD), the like, or acombination thereof.

In some embodiments, the pads 104 may be referred to as die connectors104 and may be conductive pillars (for example, comprising a metal suchas copper). The pads 104 may be formed by, for example, metaldeposition, plating, a combination thereof or the like. The active sideof the integrated circuit die 100 (including pads 104 and insulatinglayers) may be planarized by a planarization process, such as a chemicalmechanical polishing (CMP), to ensure planar surfaces for the subsequentbonding.

FIG. 1 further illustrates conductive pillars 106 formed on some of thepads 104. As illustrated the conductive pillars 106 may taper from thetop to the bottom due to the high aspect ratio and relatively smalldimensions of the pillars. The conductive pillars 106 will extendthrough the subsequently formed encapsulant 390 (see FIG. 6) and may bereferred to as through vias 106 hereinafter. As an example to form thethrough vias 106, a seed layer is formed over the active side of theintegrated circuit die, e.g., the interconnect and pads 104 asillustrated. In some embodiments, the seed layer is a metal layer, whichmay be a single layer or a composite layer comprising a plurality ofsub-layers formed of different materials. In some embodiments, the seedlayer comprises a titanium layer and a copper layer over the titaniumlayer. The seed layer may be formed using, for example, PVD or the like.A photo resist is formed and patterned on the seed layer. The photoresist may be formed by spin coating, lamination or the like and may beexposed to light for patterning. The pattern of the photo resistcorresponds to through vias. The patterning forms openings through thephoto resist to expose the seed layer. A conductive material is formedin the openings of the photo resist and on the exposed portions of theseed layer. The conductive material may be formed by plating, such aselectroplating or electroless plating, or the like. The conductivematerial may comprise a metal, like copper, nickel, titanium, tungsten,aluminum, a combination thereof or the like. The photo resist andportions of the seed layer on which the conductive material is notformed are removed. The photo resist may be removed by an acceptableashing or stripping process, such as using an oxygen plasma or the like.Once the photo resist is removed, exposed portions of the seed layer areremoved, such as by using an acceptable etching process, such as by wetor dry etching. The remaining portions of the seed layer and conductivematerial form the through vias 106.

In some embodiments, the pads 104 with the conductive pillars 106 onthem are formed with different configurations (e.g., the pads 104 withconductive pillars may not be recessed as shown, for example, by therecessed pad 312 in FIG. 4A) than the pads 104 without conductivepillars 106. In some embodiment, all of the pads 104 are formed with thesame configuration.

FIG. 2 illustrates an integrated circuit die 200 at an intermediate stepin processing. The integrated circuit die 200 may be a logic die (e.g.,central processing unit, ASIC, FPGA, microcontroller, etc.), a memorydie (e.g., a DRAM die, a Wide I/O die, a M-RAM die, a R-RAM die, a NANDdie, an SRAM die, etc.), a memory cube (e.g. HBM, HMC, etc.), a highdata rate transceiver die, a I/O interface die, a IPD die (e.g.integrated passives device), a power management die (e.g., a PMIC die),an RF die, a sensor die, an MEMS die, signal processing dies (e.g., aDSP die), a front-end die (e.g., an AFE dies), a monolithic 3Dheterogeneous chiplet stacking die, the like, or a combination thereof.In some embodiments, the integrated circuit die 100 is a logic die andthe integrated circuit die 200 is a memory die.

Before the intermediate step illustrate in FIG. 2, the integratedcircuit die 200 may be processed according to applicable manufacturingprocesses to form integrated circuits in the integrated circuit die 200.For example, the integrated circuit die 200 includes a semiconductorsubstrate 202, such as silicon, doped or undoped, or an active layer ofa semiconductor-on-insulator (SOI) substrate. The semiconductorsubstrate 102 may include other semiconductor material, such asgermanium; a compound semiconductor including silicon carbide, galliumarsenic, gallium phosphide, indium phosphide, indium arsenide, and/orindium antimonide; an alloy semiconductor including SiGe, GaAsP, AlInAs,AlGaAs, GaInAs, GaInP, and/or GaInAsP; or combinations thereof. Othersubstrates, such as multi-layered or gradient substrates, may also beused. Devices, such as transistors, diodes, capacitors, resistors, etc.,may be formed in and/or on the semiconductor substrate 102 and may beinterconnected by interconnect structures formed by, for example,metallization patterns in one or more dielectric layers on thesemiconductor substrate 202 to form an integrated circuit. Theinterconnect structures are formed using damascene and/or dual-damasceneprocess, in some embodiments.

The integrated circuit die 200 further includes through vias 204 andpads 206. The through vias 204 may extend through the semiconductorsubstrate 202 at this point in processing, or as illustrated in FIG. 2,may partially extend through the semiconductor substrate 202 at thispoint in processing. In the partial embodiment, the semiconductorsubstrate 202 may be thinned (see e.g., FIG. 11) such that the throughvias 204 may extend through the semiconductor substrate 202. The throughvias 204 may be formed, for example, by etching openings into thesubstrate 202 and then depositing a conductive material into theopenings. These openings for the through vias 204 may all be formedsimultaneously in a same process, or in separate processes. Openingsinto the substrate 202 may be formed using a suitable photolithographicmask and etching process. For example, a photoresist may be formed andpatterned over the substrate 202, and one or more etching processes(e.g., a wet etch process or a dry etch process) are utilized to removethose portions of the substrate 202 where the through vias 204 aredesired. The openings may be formed from the active side of theintegrated circuit die 200 (i.e., lower side of integrated circuit die200 in FIG. 2) by forming and patterning a mask on the active side ofthe integrated circuit die 200.

The openings may be filled with, e.g., a liner, such as a diffusionbarrier layer, an adhesion layer, or the like, and a conductivematerial. The liner may include titanium, titanium nitride, tantalum,tantalum nitride, or the like. The liner may be formed using a chemicalvapor deposition (CVD) process, such as a plasma enhanced CVD (PECVD).However, other alternative processes, such as sputtering or metalorganic chemical vapor deposition (MOCVD), may be used.

The conductive material of the through vias 204 may comprise one or moreconductive materials, copper, a copper alloy, silver, gold, tungsten,aluminum, nickel, other conductive metals, a combination thereof or thelike. The conductive material may be formed, for example, by depositinga seed layer (not shown) and using electroplating, electroless plating,or the like to deposit conductive material onto the seed layer, fillingand overfilling the openings for the through vias 204. Once the openingsfor the through vias 204 have been filled, excess liner and excessconductive material outside of the openings for the through vias 204 maybe removed through a grinding process such as chemical mechanicalpolishing (CMP), although any suitable removal process may be used. Asone of ordinary skill in the art will recognize, the above describedprocess for forming the through vias 204 is merely one method of formingthe through vias 24, and other methods are also fully intended to beincluded within the scope of the embodiments. In some embodiments, thethrough vias 204 are formed from the back side of the integrated circuitdie 200.

Although two through vias 204 are illustrated in the integrated circuitdie 200, it should be appreciated that there may be more or less throughvias 204 in each integrated circuit die 200.

The pads 206 may be copper pads or aluminum pads or a combinationthereof to which external connections are made. In some embodiments,these pads 206 may be used in a hybrid bonding configuration to bond theintegrated circuit die 200 to another die or structure. The pads 206 areon what may be referred to as the active side of the integrated circuitdie 200. The pads 206 may be formed on and electrically coupled to thethrough vias 204. One or more insulating layers 208 are also on theactive side of the integrated circuit die 200. The insulating layers 208may be inorganic or organic layers. In some embodiments, the insulatinglayers 208 are formed of a polymer, which may be a photo-sensitivematerial such as PBO, polyimide, BCB, or the like. In other embodiments,the insulating layers 208 are formed of a nitride such as siliconnitride; an oxide such as silicon oxide, PSG, BSG, BPSG; or the like.The insulating layers 208 may be formed by spin coating, lamination,CVD, the like, or a combination thereof. The active side of theintegrated circuit die 200 (including pads 206 and insulating layers208) may be planarized by a planarization process, such as a CMP, toensure planar surfaces for the subsequent bonding.

In some embodiments, the pads 206 may be referred to as die connectors206 and may be conductive pillars or vias (for example, comprising ametal such as copper, aluminum, a combination thereof). The pads 206 maybe formed by, for example, plating, or the like. In some embodiments,either one or both of the pads 104 and 206 include a solder material tobe utilized when joining the integrated circuit dies 100 and 200. Thisstructure will be described in more detail in FIGS. 4A-4O.

FIG. 3 illustrates the integrated circuit die 200 bonded to theintegrated circuit die 100 through hybrid bonding. To achieve the hybridbonding, the integrated circuit dies 100 and 200 are first pre-bonded bytheir insulating layers on their active sides (e.g., 208) by lightlypressing the integrated circuit dies 100 and 200 together. Although oneintegrated circuit die 100 and one integrated circuit die 200 areillustrated, the hybrid bonding may be performed at wafer level (e.g.chip on wafer or wafer on wafer), wherein there are multiple theintegrated circuit die 100 formed in a wafer and there are multipleintegrated circuit dies 200 identical to the illustrated integratedcircuit die 200 are pre-bonded, and arranged as rows and columns on thewafer.

After all of the integrated circuit dies 100 and 200 are pre-bonded, areflow process is performed to cause the reflow of the solder (i.e.,solder material between the pads 104 and 206) and inter-diffusion of thesolder and of the metals in at least one of the pads 104 and 206. Thereflow temperature may be lowered to lower than about 200° C. in orderto avoid the damage of the insulating layers and bonding dies. Forexample, the reflow temperature may be in the range between about 150°C. and about 200° C. The annealing time may be between about 2 hours and3 hours. In accordance of some embodiment, a thermal compression bond(TCB) may be applied to locally heat up the bonding interfaces to reducethe bonding time and the thermo-mechanical stress at the bonding jointsdue to a mismatch of coefficient of thermal expansion (CTE) among topcircuit die, bottom circuit die, and bonding tool.

Through the hybrid bonding, the pads 104 and 206 are bonded to eachother through solder bonding to form a bonding joint 300. The insulatinglayer of the integrated circuit die 100 is also bonded to the insulatinglayer 208, with bonds formed therebetween. For example, the atoms (suchas oxygen atoms) in one of the insulating layers form chemical orcovalence bonds (such as O—H bonds) with the atoms (such as hydrogenatoms) in the other one of the insulating layers. The resulting bondsbetween the insulating layers are dielectric-to-dielectric bonds, whichmay be inorganic-to-polymer, polymer-to-polymer, orinorganic-to-inorganic bonds in accordance with various embodiments.Furthermore, the surface insulating layers of two integrated circuitdies 100 and/or 200 may be different from each other (for example, withone being a polymer layer and the other being an inorganic layer), andhence there may be two types of inorganic-to-polymer,polymer-to-polymer, and inorganic-to-inorganic bonds existingsimultaneously in the same package.

FIGS. 4A, 4B, 4C, 4D, 4E, 4F, 4G, 4H, 4I, 4J, 4K, 4L, 4M, 4N, and 4Oillustrate detailed views of different configurations of a bonding joint300 from FIG. 3. In each of the illustrated configurations, theintegrated circuit dies 100 and 200 could be either the top example die(i.e., die above bonding interface 350) in FIGS. 4A-4O or the bottomexample die (i.e., die below bonding interface 350) in FIGS. 4A-4O.

FIG. 4A illustrates a bonding joint configuration 300A with dielectricbonding and a recessed bonding pad. In FIG. 4A, a first die includes asemiconductor substrate 302, dielectric layers 304, 308, and 310 on thesemiconductor substrate 302, a metallization layer 306 in the dielectriclayer 304, and a recessed bond pad 312 in the dielectric layer 310 andon the metallization layer 306. In FIG. 4A, a second die includes asemiconductor substrate 320, dielectric layers 322, 326, and 328 on thesemiconductor substrate 320, a metallization layer 324 in the dielectriclayer 322, a bond pad 330 in the dielectric layer 328 and on themetallization layer 324, and a protruded bump including layers 332 and334. Interface 350 illustrates the bonding interface between thedielectric layers 310 and 328.

In this embodiment, the dielectric layers 304, 308, 310, 322, 326, and328 are formed of a nitride such as silicon nitride; an oxide such assilicon oxide, PSG, BSG, BPSG; or the like. The dielectric layers 308and 326 may be utilized as etch stop layers when forming the bond pads312 and 330 on the respective dies and may be made from a differentmaterial composition than the surrounding dielectric layers. Thesurfaces of the dielectric layers 310 and 328 at the bonding interface350 (including their respective conductive features 330 and 312) may beplanarized by a planarization process, such as a CMP, to ensure planarsurfaces for the bonding.

The metallization layers 306 and 324 and bond pad 330 may be formed aconductive material may comprise a metal, like copper, titanium,tungsten, aluminum, or the like. The conductive material may be formedby plating, such as electroplating or electroless plating, sputtering,or the like. These structures may be formed by a damascene process andmay include a diffusion barrier layer, an adhesion layer, or the like, aseed layer, and a conductive material. The diffusion barrier layerand/or adhesion layer may include titanium, titanium nitride, tantalum,tantalum nitride, or the like. The diffusion barrier layer and/oradhesion layer may be formed using a CVD process, such as a PECVD.However, other alternative processes, such as sputtering or MOCVD, maybe used. In some embodiments, the seed layer is a metal layer, which maybe a single layer or a composite layer comprising a plurality ofsub-layers formed of different materials. In some embodiments, the seedlayer comprises a titanium layer and a copper layer over the titaniumlayer. The seed layer may be formed using, for example, PVD or the like.

The recessed bond pad 312 may include multiple layers formed in therecess of the dielectric layer 310. The layers may include a seed layer312A, a diffusion barrier layer 312B, and a conductive material layer312C. In addition, there may be a diffusion barrier layer and/or anadhesion layer between the seed layer 312A and the dielectric layer 310.

The diffusion barrier layer and/or adhesion layer may include titanium,titanium nitride, tantalum, tantalum nitride, or the like. The diffusionbarrier layer and/or adhesion layer may be formed using a CVD process,such as a PECVD. However, other alternative processes, such assputtering or MOCVD, may be used.

In some embodiments, the seed layer 312A is a metal layer, which may bea single layer or a composite layer comprising a plurality of sub-layersformed of different materials. In some embodiments, the seed layer 312Acomprises a titanium layer and a copper layer over the titanium layer.The seed layer 312A may be formed using, for example, PVD or the like.

In some embodiments, the diffusion barrier layer 312B comprises a layerof nickel. The diffusion barrier layer 312B may be formed using, forexample, PVD or the like. The diffusion barrier layer 312B providesdiffusion protection such that the solder material 334 does not diffuseinto the metallization layer 306. Other materials may be used in theplace of the diffusion barrier as long as they provide an appropriateamount of diffusion protection.

The conductive material layer 312C may comprise one or more conductivematerials, copper, a copper alloy, silver, gold, tungsten, aluminum,nickel, other conductive metals, or the like. The conductive materiallayer 312C may be formed, for example, by electroplating, electrolessplating, or the like to deposit a conductive material. The layers 312A,312B, and 312C of the bond pad 312 do not fill the recess in thedielectric layer 310 such that the bond pad 312 is recessed in thedielectric layer 310. This recessed bond pad 312 can allow for a thinnerpackage by reducing the standoff of the bonded package. After theformation of the conductive material layer 312C, excess portions of thelayers 312A, 312B, and 312C outside of the recess (e.g., along an uppersurface of dielectric layer 310 before the dies are bonded) may beremoved through a grinding process such as CMP. In this embodiment, thecombined thickness of the layers 312A, 312B, and 312C is less than thethickness of the dielectric layer 310.

The bump layers 332 and 334 include a diffusion barrier layer 332 and asolder layer 334. The diffusion barrier layer 332 may be formed on thebond pad 330. In some embodiments, the diffusion barrier layer 332comprises a layer of nickel. The diffusion barrier layer 332 may beformed using, for example, PVD or the like. The diffusion barrier layer332 provides diffusion protection such that the solder material 334 doesnot diffuse into the pad/via 330. Other materials may be used in theplace of the diffusion barrier as long as they provide an appropriateamount of diffusion protection.

The solder layer 334 may be formed on the diffusion barrier layer 332.The solder layer 334 may be formed of a solder material includingcopper, aluminum, gold, nickel, silver, palladium, tin, the like, or acombination thereof. The solder layer 334 may be formed by evaporation,electroplating, printing, solder transfer, ball placement, or the like.The solder layer 334 is bonded to the recessed bond pad through a solderreflow process (described in detail above) or a thermal compression bondprocess. The solder layer 334 has a lower reflow temperature than boththe conductive material layer 312C of the bond pad 312 and the pad/via330. This allows for a lower reflow temperature to be used when bondingthe dies together.

As illustrated, the bonding joints 300A-3300 of FIGS. 4A-4O include avoid or gap 336 surrounding the solder layer 334 and between the bondpad 312 and the dielectric layer 322/328. This void/gap 336 can remainunfilled and be visible in the final product.

FIG. 4B illustrates another configuration 300B of the bonding joint 300of FIG. 3. This embodiment is similar to the previous embodiment of FIG.4A except that in this embodiment, the bonding interface 350 includespolymer layers 340 and 342 instead of dielectric layers and thus itincludes polymer bonding. Details regarding this embodiment that aresimilar to those for the previously described embodiment will not berepeated herein.

In this embodiment, each of the dies includes a polymer layer as thebonding layer. The polymer layer 340 is formed on the first die and thepolymer layer 342 is formed on the second die. The polymer layers 340and 342 may be a photo-sensitive material such as PBO, polyimide, BCB,or the like. The polymer layers 340 and 342 may be formed by spincoating, lamination, the like, or a combination thereof.

FIG. 4C illustrates another configuration 300C of the bonding joint 300of FIG. 3. This embodiment is similar to the previous embodiment of FIG.4B except that in this embodiment, the bond pad 312 is not recessed intoan insulating layer. Details regarding this embodiment that are similarto those for the previously described embodiment will not be repeatedherein.

In this embodiment, the bond pad 312 is not recessed but issubstantially planar across the metallization layer 306. The polymerlayer 340 extends above the upper surface of the bonding pad 312 and thepolymer layer 342 extends from the dielectric layer 322 of the seconddie such that the bump layers 332 and 334 have space between the bondingpad 312 and the pad/via 324.

FIG. 4D illustrates another configuration 300D of the bonding joint 300of FIG. 3. This embodiment is similar to the previous embodiment of FIG.4A except that in this embodiment, the bonding interface 350 is a solderbonding but not a dielectric bonding as the dielectric layers 310 and328 are separated from each other. Details regarding this embodimentthat are similar to those for the previously described embodiment willnot be repeated herein.

In this embodiment, the dielectric layers 310 and 328 of the dies arespaced apart from each other after the bonding process. This embodimentis not necessarily ideal as the standoff height is greater and thebonding strength may be reduced as compared to the other embodiments.

FIG. 4E illustrates another configuration 300E of the bonding joint 300of FIG. 3. This embodiment is similar to the previous embodiment of FIG.4A except that in this embodiment, the metallization layer 306 is overand electrically coupled to through via 204/through via 466 (see FIG. 15for 466). Details regarding this embodiment that are similar to thosefor the previously described embodiment will not be repeated herein.

In this embodiment, the through via 204/through via 466 is formedthrough one of the integrated circuit dies 100 and/or 200.

FIG. 4F illustrates another configuration 300F of the bonding joint 300of FIG. 3. This embodiment is similar to the previous embodiment of FIG.4E except that in this embodiment, the metallization layer 306 isomitted and the through via 204/through via 466 is directly coupled tothe recessed pad 312. Details regarding this embodiment that are similarto those for the previously described embodiment will not be repeatedherein.

In this embodiment, the width of the through via 204/through via 466adjoining the recessed pad 312 is less than the width of the recessedpad 312.

FIG. 4G illustrates another configuration 300G of the bonding joint 300of FIG. 3. This embodiment is similar to the previous embodiment of FIG.4F except that in this embodiment, the width of the through via204/through via 466 adjoining the recessed pad 312 is greater than thewidth of the recessed pad 312. Details regarding this embodiment thatare similar to those for the previously described embodiment will not berepeated herein.

FIG. 4H illustrates another configuration 300H of the bonding joint 300of FIG. 3. This embodiment is similar to the previous embodiment of FIG.4F except that in this embodiment, the width of the through via204/through via 466 adjoining the recessed pad 312 is equal to the widthof the recessed pad 312. Details regarding this embodiment that aresimilar to those for the previously described embodiment will not berepeated herein.

FIG. 4I illustrates another configuration 300I of the bonding joint 300of FIG. 3. This embodiment is similar to the previous embodiment of FIG.4F except that in this embodiment, there is more than one through via204/through via 466 adjoining the recessed pad 312. Details regardingthis embodiment that are similar to those for the previously describedembodiment will not be repeated herein.

FIG. 4J illustrates another configuration 300J of the bonding joint 300of FIG. 3. This embodiment is similar to the previous embodiment of FIG.4E except that in this embodiment, there is more than one through via204/through via 466 adjoining the recessed pad 312. Details regardingthis embodiment that are similar to those for the previously describedembodiment will not be repeated herein.

FIG. 4K illustrates another configuration 300K of the bonding joint 300of FIG. 3. This embodiment is similar to the previous embodiment of FIG.4J except that in this embodiment, the width of the through via204/through via 466 adjoining the recessed pad 312 is equal to the widthof the recessed pad 312. Details regarding this embodiment that aresimilar to those for the previously described embodiment will not berepeated herein.

FIG. 4L illustrates another configuration 300L of the bonding joint 300of FIG. 3. This embodiment is similar to the previous embodiment of FIG.4F except that in this embodiment, the recessed pad 312 is omitted andsolder material 334 is directly coupled to the through via 204/throughvia 466. Details regarding this embodiment that are similar to those forthe previously described embodiment will not be repeated herein.

In this embodiment, the through via 204/through via 466 may be recessedsuch that some portion of the solder material 334 extend below a topmostsurface of the through via 204/through via 466 and/or the surface of thedielectric layer 304. In some embodiments, the width of the void 336 isgreater than the width of through via 204/through via 466 adjoining thesolder material 334.

FIG. 4M illustrates another configuration 300M of the bonding joint 300of FIG. 3. This embodiment is similar to the previous embodiment of FIG.4L except that in this embodiment, the width of the void 336 is lessthan the width of through via 204/through via 466 adjoining the soldermaterial 334. Details regarding this embodiment that are similar tothose for the previously described embodiment will not be repeatedherein.

FIG. 4N illustrates another configuration 300N of the bonding joint 300of FIG. 3. This embodiment is similar to the previous embodiment of FIG.4L except that in this embodiment, the width of the void 336 is equal tothe width of through via 204/through via 466 adjoining the soldermaterial 334. Details regarding this embodiment that are similar tothose for the previously described embodiment will not be repeatedherein.

FIG. 4O illustrates another configuration 300O of the bonding joint 300of FIG. 3. This embodiment is similar to the previous embodiment of FIG.4J except that in this embodiment, the recessed pad 312 is omitted andsolder material 334 is directly coupled to the metallization layer 306.Details regarding this embodiment that are similar to those for thepreviously described embodiment will not be repeated herein.

In each of the configurations of FIGS. 4A, 4B, 4C, 4E-4O the hybridbonding includes pre-bonding insulating layers (e.g., 310, 328, 340,and/or 342) on the active sides of the dies by lightly pressing theintegrated circuit dies and together. After the pre-bonding, the reflowprocess is performed to cause the reflow of the solder layer 334.

In FIG. 5, an encapsulant 390 is formed on the various components ofFIG. 3. The encapsulant 390 may be a molding compound, an epoxy, anoxide, or the like, and may be applied by compression molding, transfermolding, lamination, flowable CVD, or the like. In some embodiments, theencapsulant may be an oxide layer such as, for example silicon oxide,tetraethylorthosilicate (TEOS) silicon oxide, or the like. In someembodiments, the encapsulant may be a nitride layer such as, for examplesilicon nitride, or the like. In some embodiments, the encapsulant maybe a composite of organic and inorganic encapsulant or the like. Theencapsulant 390 may be formed over the wafer including the integratedcircuit die 100 such that the conductive pillars 106 and the integratedcircuit dies 200 are buried or covered. The encapsulant 390 may then becured. The semiconductor substrate 102 of the integrated circuit dies100 may have a thickness T1 of about 775 μm.

In FIG. 6, the semiconductor substrate 102 may be thinned to a thicknessT2 which is less than the thickness T1. The thinning process may includea grinding process, such as a mechanical grinding, CMP, an etchingprocess, or a combination thereof. In some embodiments, the thickness T2is in a range from about 50 μm to about 150 μm.

After the thinning process, the package including the integrated circuitdies 100 and 200 may be singulated, such as by sawing or dicing to formmultiple packages 392 with each package 392 including at least oneintegrated circuit die 100 and one integrated circuit die 200. In someembodiments, the singulating occurs in scribe line regions betweenpackage regions.

FIG. 7 illustrates a carrier substrate 400, a release layer 402 formedon the carrier substrate 400, and a dielectric layer 404 formed on therelease layer 402. The carrier substrate 400 may be a glass carriersubstrate, a ceramic carrier substrate, or the like. The carriersubstrate 400 may be a wafer, such that multiple packages can be formedon the carrier substrate 400 simultaneously. The release layer 402 maybe formed of a polymer-based material, which may be removed along withthe carrier substrate 400 from the overlying structures that will beformed in subsequent steps. In some embodiments, the release layer 402is an epoxy-based thermal-release material, which loses its adhesiveproperty when heated, such as a light-to-heat-conversion (LTHC) releasecoating. In other embodiments, the release layer 402 may be anultra-violet (UV) glue, which loses its adhesive property when exposedto UV lights. The release layer 402 may be dispensed as a liquid andcured, may be a laminate film laminated onto the carrier substrate 400,or may be the like. The top surface of the release layer 402 may beleveled and may have a high degree of coplanarity.

The dielectric layer 404 is formed on the release layer 402. The bottomsurface of the dielectric layer 404 may be in contact with the topsurface of the release layer 402. In some embodiments, the dielectriclayer 404 is formed of a polymer, such as PBO, polyimide, BCB, or thelike. In other embodiments, the dielectric layer 404 is formed of anitride such as silicon nitride; an oxide such as silicon oxide, PSG,BSG, BPSG, or the like. The dielectric layer 404 may be formed by anyacceptable deposition process, such as spin coating, chemical vapordeposition CVD, laminating, or the like, or a combination thereof. Insome embodiments, one or more metallization patterns are formed on or inthe dielectric layer 404 to form a redistribution structure. Thisredistribution structure may be referred to as a back-sideredistribution structure.

Further in FIG. 7, electrical connectors 406 are formed. The electricalconnectors 406 will extend through the subsequently formed encapsulant408 (see FIG. 9) and may be referred to as through vias 406 hereinafter.As an example to form the through vias 406, a seed layer is formed overthe underlying structure, e.g., the dielectric layer 404. In someembodiments, the seed layer is a metal layer, which may be a singlelayer or a composite layer comprising a plurality of sub-layers formedof different materials. In some embodiments, the seed layer comprises atitanium layer and a copper layer over the titanium layer. The seedlayer may be formed using, for example, PVD or the like. A photo resistis formed and patterned on the seed layer. The photo resist may beformed by spin coating, lamination or the like and may be exposed tolight for patterning. The pattern of the photo resist corresponds tothrough vias 406. The patterning forms openings through the photo resistto expose the seed layer. A conductive material is formed in theopenings of the photo resist and on the exposed portions of the seedlayer. The conductive material may be formed by plating, such aselectroplating or electroless plating, or the like. The conductivematerial may comprise a metal, like copper, titanium, tungsten,aluminum, or the like. The photo resist and portions of the seed layeron which the conductive material is not formed are removed. The photoresist may be removed by an acceptable ashing or stripping process, suchas using an oxygen plasma or the like. Once the photo resist is removed,exposed portions of the seed layer are removed, such as by using anacceptable etching process, such as by wet or dry etching. The remainingportions of the seed layer and conductive material form the through vias406.

In FIG. 8, package 392 is attached to the release layer 402. Althoughone package 392 is illustrated as being attached, it should beappreciated that more or less packages 392 may be attached in eachpackage region. Although not shown, the package 392 may be attached byan adhesive layer (not shown). The adhesive may be any suitableadhesive, epoxy, die attach film (DAF), or the like.

In FIG. 9, an encapsulant 408 is formed on the various components. Theencapsulant 408 may be a molding compound, epoxy, or the like, and maybe applied by compression molding, lamination, transfer molding, or thelike. The encapsulant 408 may be formed over the carrier substrate 400such that the electrical connectors 406 and the package 392 are buriedor covered. The encapsulant 408 may then be cured. The encapsulants 408and 390 may be made of the same material or different materials.

In FIG. 10, the encapsulant 408 can undergo a grinding process to exposethe electrical connectors 406, conductive pillars 106, and through vias204. Surfaces of the electrical connectors 406, conductive pillars 106,through vias 204, semiconductor substrate 202, and encapsulant 408 arelevel after the grinding process. In some embodiments, the grinding maybe omitted, for example, if the electrical connectors 406, theconductive pillars 106, and the through vias 204 are already exposed.The electrical connectors 406 and the conductive pillars 106 may bereferred to as through vias 406 and 106, respectively, hereinafter.

In FIG. 11, a front-side redistribution structure 410 is formed. Thefront-side redistribution structure 410 includes one or more dielectriclayers 414 and one or more metallization patterns 412.

The formation of the front-side redistribution structure 410 may beginby depositing dielectric layer 414 on the encapsulant 408, through vias406, through vias 204, and through vias 106. In some embodiments, thethrough vias 106 and 204 may have conductive pads formed on their topsto help the overlying metallization patterns 412 land on and beelectrically coupled with the respective through vias 106 and 204 (see,e.g., FIG. 23 with pads 494). In some embodiments, the dielectric layer414 is formed of a polymer, which may be a photo-sensitive material suchas PBO, polyimide, BCB, or the like, that may be patterned using alithography mask. In other embodiments, the dielectric layer 414 isformed of a nitride such as silicon nitride; an oxide such as siliconoxide, PSG, BSG, BPSG; or the like. The dielectric layer 414 may beformed by spin coating, lamination, CVD, the like, or a combinationthereof.

Next, the dielectric layer 414 is then patterned. The patterning formsopenings to expose portions of the through vias 406, 106, and 204. Thepatterning may be by an acceptable process, such as by exposing thedielectric layer 414 to light when the dielectric layer 414 is aphoto-sensitive material or by ablation using, for example, a laserablation or by etching using, for example, an anisotropic etch. If thedielectric layer 414 is a photo-sensitive material, the dielectric layer414 can be developed after the exposure.

Next, metallization pattern 412 with vias is formed on the dielectriclayer 414. As an example to form metallization pattern 412, a seed layer(not shown) is formed over the dielectric layer 414 and in openingsthrough the dielectric layer 414. In some embodiments, the seed layer isa metal layer, which may be a single layer or a composite layercomprising a plurality of sub-layers formed of different materials. Insome embodiments, the seed layer comprises a titanium layer and a copperlayer over the titanium layer. The seed layer may be formed using, forexample, PVD or the like. A photo resist is then formed and patterned onthe seed layer. The photo resist may be formed by spin coating or thelike and may be exposed to light for patterning. The pattern of thephoto resist corresponds to the metallization pattern 412. Thepatterning forms openings through the photo resist to expose the seedlayer. A conductive material is formed in the openings of the photoresist and on the exposed portions of the seed layer. The conductivematerial may be formed by plating, such as electroplating or electrolessplating, or the like. The conductive material may comprise a metal, likecopper, titanium, tungsten, aluminum, or the like. Then, the photoresist and portions of the seed layer on which the conductive materialis not formed are removed. The photo resist may be removed by anacceptable ashing or stripping process, such as using an oxygen plasmaor the like. Once the photo resist is removed, exposed portions of theseed layer are removed, such as by using an acceptable etching process,such as by wet or dry etching. The remaining portions of the seed layerand conductive material form the metallization pattern 412 and vias. Thevias are formed in openings through the dielectric layer 414 to, e.g.,the through vias 406, 106, and 204.

This process may be repeated with more dielectric layers 414 and moremetallization patterns and vias 412 to continue the formation of theredistribution structure 410. The materials and processes used to formthese layers of the redistribution structure 410 may be similar to thatdescribed above and the description is not repeated herein. In someembodiments, the redistribution structure 410 is formed by a damasceneprocess. In some embodiments, some of the layers of the redistributionstructure 410 are formed by a dual damascene process and other layersare formed by the process described in the preceding paragraphs, forexample, semi-additive process (SAP)

The front-side redistribution structure 410 is shown as an example. Moreor fewer dielectric layers and metallization patterns may be formed inthe front-side redistribution structure 410. If fewer dielectric layersand metallization patterns are to be formed, steps and process discussedabove may be omitted. If more dielectric layers and metallizationpatterns are to be formed, steps and processes discussed above may berepeated. One having ordinary skill in the art will readily understandwhich steps and processes would be omitted or repeated.

In FIG. 12, pads (not shown) are formed on an exterior side of thefront-side redistribution structure 410 and conductive connectors 416are formed on the pads. The pads are used to couple to conductiveconnectors 416 and may be referred to as under bump metallurgies (UBMs).The pads may be formed through openings in the uppermost dielectriclayer 414 of the redistribution structure 410 to the uppermostmetallization pattern 412. As an example to form the pads, a seed layer(not shown) is formed over the dielectric layer 414. In someembodiments, the seed layer is a metal layer, which may be a singlelayer or a composite layer comprising a plurality of sub-layers formedof different materials. In some embodiments, the seed layer comprises atitanium layer and a copper layer over the titanium layer. The seedlayer may be formed using, for example, PVD or the like. A photo resistis then formed and patterned on the seed layer. The photo resist may beformed by spin coating or the like and may be exposed to light forpatterning. The pattern of the photo resist corresponds to the pads. Thepatterning forms openings through the photo resist to expose the seedlayer. A conductive material is formed in the openings of the photoresist and on the exposed portions of the seed layer. The conductivematerial may be formed by plating, such as electroplating or electrolessplating, or the like. The conductive material may comprise a metal, likecopper, titanium, tungsten, aluminum, or the like. Then, the photoresist and portions of the seed layer on which the conductive materialis not formed are removed. The photo resist may be removed by anacceptable ashing or stripping process, such as using an oxygen plasmaor the like. Once the photo resist is removed, exposed portions of theseed layer are removed, such as by using an acceptable etching process,such as by wet or dry etching. The remaining portions of the seed layerand conductive material form the pads. In the embodiment, where the padsare formed differently, more photo resist and patterning steps may beutilized.

Further in FIG. 12, conductive connectors 416 are formed on thepads/UBMs. The conductive connectors 416 may be ball grid array (BGA)connectors, solder balls, metal pillars, controlled collapse chipconnection (C4) bumps, micro bumps, electroless nickel-electrolesspalladium-immersion gold technique (ENEPIG) formed bumps, or the like.The conductive connectors 416 may include a conductive material such assolder, copper, aluminum, gold, nickel, silver, palladium, tin, thelike, or a combination thereof. In some embodiments, the conductiveconnectors 416 are formed by initially forming a layer of solder throughsuch commonly used methods such as evaporation, electroplating,printing, solder transfer, ball placement, or the like. Once a layer ofsolder has been formed on the structure, a reflow may be performed inorder to shape the material into the desired bump shapes. In anotherembodiment, the conductive connectors 416 are metal pillars (such as acopper pillar) formed by a sputtering, printing, electro plating,electroless plating, CVD, or the like. The metal pillars may be solderfree and have substantially vertical sidewalls. In some embodiments, ametal cap layer (not shown) is formed on the top of the metal pillarconnectors 416. The metal cap layer may include nickel, tin, tin-lead,gold, silver, palladium, indium, nickel-palladium-gold, nickel-gold, thelike, or a combination thereof and may be formed by a plating process.

In FIG. 13, a carrier substrate de-bonding is performed to detach(de-bond) the carrier substrate 400 from the dielectric layer 404. Thefirst package 420 are thereby formed in each of the package regions ofthe carrier. In accordance with some embodiments, the de-bondingincludes projecting a light such as a laser light or an UV light on therelease layer 402 so that the release layer 402 decomposes under theheat of the light and the carrier substrate 400 can be removed. Openingsare formed through the dielectric layer 404 to expose portions of themetallization pattern through vias 406. The openings may be formed, forexample, using laser drilling, etching, or the like.

FIG. 14 illustrates a cross-sectional view of a package structure, inaccordance with some embodiments. The package structure may be referredto a package-on-package (PoP) structure. In FIG. 14, a second package450 is attached to the first package 420. The second package 450includes a substrate 430 and one or more stacked dies 440 (440A and440B) coupled to the substrate 430. Although a singular stack of dies440 (440A and 440B) is illustrated, in other embodiments, a plurality ofstacked dies 440 (each having one or more stacked dies) may be disposedside by side coupled to a same surface of the substrate 430. Thesubstrate 430 may be made of a semiconductor material such as silicon,germanium, diamond, or the like. In some embodiments, compound materialssuch as silicon germanium, silicon carbide, gallium arsenic, indiumarsenide, indium phosphide, silicon germanium carbide, gallium arsenicphosphide, gallium indium phosphide, combinations of these, and thelike, may also be used. Additionally, the substrate 430 may be asilicon-on-insulator (SOI) substrate. Generally, an SOI substrateincludes a layer of a semiconductor material such as epitaxial silicon,germanium, silicon germanium, SOI, silicon germanium on insulator(SGOI), or combinations thereof. The substrate 430 is, in onealternative embodiment, based on an insulating core such as a fiberglassreinforced resin core. One example core material is fiberglass resinsuch as FR4. Alternatives for the core material includebismaleimide-triazine (BT) resin, or alternatively, other printedcircuit board (PCB) materials or films. Build up films such as Ajinomotobuild-up film (ABF) or other laminates may be used for substrate 430.

The substrate 430 may include active and passive devices (not shown). Asone of ordinary skill in the art will recognize, a wide variety ofdevices such as transistors, capacitors, resistors, combinations ofthese, and the like may be used to generate the structural andfunctional requirements of the design for the second package 450. Thedevices may be formed using any suitable methods.

The substrate 430 may also include metallization layers (not shown) andthrough vias 432. The metallization layers may be formed over the activeand passive devices and are designed to connect the various devices toform functional circuitry. The metallization layers may be formed ofalternating layers of dielectric (e.g., low-k dielectric material) andconductive material (e.g., copper) with vias interconnecting the layersof conductive material and may be formed through any suitable process(such as deposition, damascene, dual damascene, or the like). In someembodiments, the substrate 430 is substantially free of active andpassive devices.

The substrate 430 may have bond pads 434 on a first side the substrate430 to couple to the stacked dies 440, and bond pads 436 on a secondside of the substrate 430, the second side being opposite the first sideof the substrate 430, to couple to the conductive connectors 438. Insome embodiments, the bond pads 434 and 436 are formed by formingrecesses (not shown) into dielectric layers (not shown) on the first andsecond sides of the substrate 430. The recesses may be formed to allowthe bond pads 434 and 436 to be embedded into the dielectric layers. Inother embodiments, the recesses are omitted as the bond pads 434 and 436may be formed on the dielectric layer. In some embodiments, the bondpads 434 and 436 include a thin seed layer (not shown) made of copper,titanium, nickel, gold, palladium, the like, or a combination thereof.The conductive material of the bond pads 434 and 436 may be depositedover the thin seed layer. The conductive material may be formed by anelectro-chemical plating process, an electroless plating process, CVD,ALD, PVD, the like, or a combination thereof. In an embodiment, theconductive material of the bond pads 434 and 436 is copper, tungsten,aluminum, silver, gold, the like, or a combination thereof.

In an embodiment, the bond pads 434 and 436 are UBMs that include threelayers of conductive materials, such as a layer of titanium, a layer ofcopper, and a layer of nickel. However, one of ordinary skill in the artwill recognize that there are many suitable arrangements of materialsand layers, such as an arrangement of chrome/chrome-copperalloy/copper/gold, an arrangement of titanium/titanium tungsten/copper,or an arrangement of copper/nickel/gold, that are suitable for theformation of the bond pads 434 and 436. Any suitable materials or layersof material that may be used for the bond pads 434 and 436 are fullyintended to be included within the scope of the current application. Insome embodiments, the through vias 432 extend through the substrate 430and couple at least one bond pad 434 to at least one bond pad 436.

In the illustrated embodiment, the stacked dies 440 are coupled to thesubstrate 430 by wire bonds 442, although other connections may be used,such as conductive bumps. In an embodiment, the stacked dies 440 arestacked memory dies. For example, the stacked dies 440 may be memorydies such as low-power (LP) double data rate (DDR) memory modules, suchas LPDDR1, LPDDR2, LPDDR3, LPDDR4, or the like memory modules.

The stacked dies 440 and the wire bonds 442 may be encapsulated by amolding material 444. The molding material 444 may be molded on thestacked dies 440 and the wire bonds 442, for example, using compressionmolding. In some embodiments, the molding material 444 is a moldingcompound, a polymer, an epoxy, silicon oxide filler material, the like,or a combination thereof. A curing step may be performed to cure themolding material 444, wherein the curing may be a thermal curing, a UVcuring, the like, or a combination thereof.

In some embodiments, the stacked dies 440 and the wire bonds 442 areburied in the molding material 444, and after the curing of the moldingmaterial 444, a planarization step, such as a grinding, is performed toremove excess portions of the molding material 444 and provide asubstantially planar surface for the second package 450.

After the second package 450 is formed, the second package 450 ismechanically and electrically bonded to the first package 420 by way ofconductive connectors 438, the bond pads 436, and the through vias 406(or backside redistribution structure if present). In some embodiments,the stacked dies 440 may be coupled to the package 392 through the wirebonds 442, the bond pads 434 and 436, through vias 432, the conductiveconnectors 438, through vias 406, and redistribution structure 410.

The conductive connectors 438 may be similar to the conductiveconnectors 416 described above and the description is not repeatedherein, although the conductive connectors 438 and the conductiveconnectors 416 need not be the same. The conductive connectors 438 maybe disposed on an opposing side of the substrate 430 as the stacked dies440. In some embodiments, a solder resist (not separately labeled) mayalso be formed on the side of the substrate opposing the stacked dies440. The conductive connectors 438 may be disposed in openings in thesolder resist to be electrically and mechanically coupled to conductivefeatures (e.g., the bond pads 436) in the substrate 430. The solderresist may be used to protect areas of the substrate 430 from externaldamage.

In some embodiments, before bonding the conductive connectors 438, theconductive connectors 438 are coated with a flux (not shown), such as ano-clean flux. The conductive connectors 438 may be dipped in the fluxor the flux may be jetted onto the conductive connectors 438. In anotherembodiment, the flux may be applied to the surfaces of the through vias406 (or backside redistribution structure if present).

In some embodiments, the conductive connectors 438 may have an optionalepoxy flux (not shown) formed thereon before they are reflowed with atleast some of the epoxy portion of the epoxy flux remaining after thesecond package 450 is attached to the first package 420.

An underfill (not shown) may be formed between the first package 420 andthe second package 450 and surrounding the conductive connectors 438.The underfill may reduce stress and protect the joints resulting fromthe reflowing of the conductive connectors 438. The underfill may beformed by a capillary flow process after the second package 450 isattached or may be formed by a suitable deposition method before thesecond package 450 is attached. In embodiments where the epoxy flux isformed, it may act as the underfill.

The bonding between the second package 450 and the first package 420 maybe a solder bonding. In an embodiment, the second package 450 is bondedto the first package 420 by a reflow process. During this reflowprocess, the conductive connectors 438 are in contact with the bond pads436 and the through vias 406 (or backside redistribution structure ifpresent) to physically and electrically couple the second package 450 tothe first package 420. After the bonding process, an intermetalliccompound (IMC, not shown) may form at the interface of the through vias406 (or backside redistribution structure if present) and the conductiveconnectors 438 and also at the interface between the conductiveconnectors 438 and the bond pads 436 (not shown). In an embodiment,after the bonding process, a underfill materials may be applied to coverthe bonding conductive connectors to provide an extra protection againstadverse environment conditions, for example, moisture, particle, andchemical corrosion or the like.

A singulation process is performed by sawing along scribe line regions,e.g., between the package regions. The resulting, singulated first andsecond packages 420 and 450 are from one of the package regions. In someembodiments, the singulation process is performed after the secondpackage 450 is attached to the first package 420. In other embodiments(not shown), the singulation process is performed before the secondpackage 450 is attached to the first package 420, such as after thecarrier substrate 400 is de-bonded.

Further processing may be performed on the package structure of FIG. 15.For example, the package structure of FIG. 15 may be mounted to apackage substrate using the conductive connectors 416.

FIGS. 15 through 21 illustrate cross-sectional views of another packagestructure in accordance with some embodiments. The embodiment in FIGS.15 through 21 is similar to the embodiment illustrated in FIGS. 1through 14 except that this embodiment includes through vias 466 in theintegrated circuit die 100 and the integrated circuit die 200 does notinclude through vias. In addition, the integrated circuit dies 100 and200 are reverse oriented in the package structure, e.g., integratedcircuit die 100 is over integrated circuit die 200 when they areattached to the carrier substrate 400 (see FIG. 18). Details regardingthis embodiment that are similar to those for the previously describedembodiment will not be repeated herein.

In FIG. 15, the integrated circuit die 100 is illustrated includingthrough vias 466. Details regarding this embodiment of the integratedcircuit die 100 that are similar to those for the previously describedintegrated circuit die 100 embodiment will not be repeated herein.

In this embodiment, the through vias 466 extend from the pad 104 on theactive side of integrated circuit die 100 into the semiconductorsubstrate 102 of the integrated circuit die 100. The formation of thethrough vias 466 may be similar to the through vias 204 of theintegrated circuit die 200 in the previous embodiment and thedescription is not repeated herein.

Although two through vias 466 are illustrated in the integrated circuitdie 100, it should be appreciated that there may be more or less throughvias 466 in each integrated circuit die 100.

FIG. 16 illustrates further processing on the structure of FIG. 15. Theprocessing between these two figures is similar to the processingillustrated and described above in reference to FIGS. 2 and 3 with FIG.3 being an equivalent intermediate stage as FIG. 6 and the descriptionsare not repeated herein.

In FIG. 16, the integrated circuit dies 100 and 200 are bonded togetherwith bonding joints 300. The bonding joints 300 can be any of thebonding joint configurations 300A-300O in FIGS. 4A-4O.

FIG. 17 illustrates further processing on the structure of FIG. 16. Theprocessing between these two figures is similar to the processingillustrated and described above in reference to FIGS. 3 through 5 withFIG. 5 being an equivalent intermediate stage as FIG. 17 and thedescriptions are not repeated herein. The bonded integrated circuit dies100 and 200 are encapsulated with encapsulant 464 to form a package 470.

FIG. 18 illustrates the attaching of the package 470 on a carriersubstrate 400 similar to that described above in FIGS. 7 and 8 and thedescriptions are not repeated herein. In FIG. 18, the package 470 isattached to the carrier with the integrated circuit die 200 nearer tothe carrier substrate than the integrated circuit die 100.

FIG. 19 illustrates further processing on the structure of FIG. 18. Theprocessing between these two figures is similar to the processingillustrated and described above in reference to FIGS. 9 and 10 with FIG.10 being an equivalent intermediate stage as FIG. 19 and thedescriptions are not repeated herein. The package 470 is encapsulatedwith encapsulant 472 and the upper surface is planarized.

In FIG. 19, the encapsulant 472 can undergo a grinding process to exposethe electrical connectors 406 and through vias 466. Surfaces of theelectrical connectors 406, through vias 466, semiconductor substrate102, and encapsulant 472 are level after the grinding process.

FIG. 20 illustrates further processing on the structure of FIG. 19. Theprocessing between these two figures is similar to the processingillustrated and described above in reference to FIGS. 10 and 11 withFIG. 11 being an equivalent intermediate stage as FIG. 20 and thedescriptions are not repeated herein. In FIG. 20, the redistributionstructure 410 is formed to be over and electrically coupled to thethrough vias 406 and through vias 466.

FIG. 21 illustrates further processing on the structure of FIG. 20. Theprocessing between these two figures is similar to the processingillustrated and described above in reference to FIGS. 12 through 14 withFIG. 14 being an equivalent intermediate stage as FIG. 21 and thedescriptions are not repeated herein. In FIG. 21, a second package 450is bonded to package structure 476 of FIG. 20.

Further processing may be performed on the package structure of FIG. 21.For example, the package structure of FIG. 21 may be mounted to apackage substrate using the conductive connectors 416.

FIGS. 22 through 28 illustrate cross-sectional views of another packagestructure in accordance with some embodiments. The embodiment in FIGS.22 through 28 is similar to the embodiment illustrated in FIGS. 15through 21 except that this embodiment has the integrated circuit dies100 and 200 bonded face-to-back instead of face-to-face. In addition,the integrated circuit dies 100 includes die connectors 488 and aninsulating layer 490 on the pads 104 on the active side of theintegrated circuit die 100. These die connectors 488 and insulatinglayer 490 can protect the pads 104 during a subsequent planarizationprocess. Details regarding this embodiment that are similar to those forthe previously described embodiment will not be repeated herein.

The die connectors 488 may be formed of similar materials and by similarprocesses as the pads 104 described above and the description is notrepeated herein. In this embodiment, the die connectors could be copperpillars and the pads 104 could be aluminum contact pads. The insulatinglayer 490 could be similar to the insulating layer 208 described aboveand the description is not repeated herein.

In FIG. 23, the active side of the integrated circuit die 100 isattached to a carrier substrate 498. The carrier substrate 498 issimilar to the carrier substrate 400 described above and the descriptionis not repeated herein. The backside of the integrated circuit die 100is thinned to expose the through vias 466. The thinning can be similarto the thinning process described above in FIG. 6 and the description isnot repeated herein. After the thinning process, insulating layers 492and 496 and pads 494 are formed on the backside of the integratedcircuit die 100. The insulating layers 492 and 496 and pads 494 will beutilized in the bonding of the integrated circuit die 100 to theintegrated circuit die 200. The pads 494 are electrically coupled to theexposed through vias 466. The pads 494 can be formed of similarmaterials and processes as the pads 104 described above and thedescription is not repeated herein. The insulating layers 492 and 496can be formed of similar materials and processes as insulating layer 208described above and the description is not repeated herein.

In FIG. 24, the integrated circuit die 100 is bonded to the integratedcircuit die 200. The bonding was described in FIGS. 2 and 3 above andthe descriptions are not repeated herein. In FIG. 24, the integratedcircuit dies 100 and 200 are bonded together with bonding joints 300.The bonding joints 300 can be any of the bonding joint configurations300A-300O in FIGS. 4A-4O.

FIG. 25 illustrates further processing on the structure of FIG. 24. Theprocessing between these two figures is similar to the processingillustrated and described above in reference to FIGS. 3 through 5 withFIG. 5 being an equivalent intermediate stage as FIG. 25 and thedescriptions are not repeated herein. The bonded integrated circuit dies100 and 200 are encapsulated with encapsulant 499 to form a package 500.

FIG. 26 illustrates the attaching of the package 500 on a carriersubstrate 400 similar to that described above in FIGS. 7 and 8 and thedescriptions are not repeated herein. In FIG. 26, the package 500 isattached to the carrier with the integrated circuit die 200 nearer tothe carrier substrate than the integrated circuit die 100.

FIG. 26 illustrates further processing on the structure of FIG. 25. Theprocessing between these two figures is similar to the processingillustrated and described above in reference to FIGS. 9 and 10 with FIG.10 being an equivalent intermediate stage as FIG. 26 and thedescriptions are not repeated herein. The package 500 is encapsulatedwith encapsulant 502 and the upper surface is planarized.

In FIG. 26, the encapsulant 502 can undergo a grinding process to exposethe electrical connectors 406 and die connectors 488. Surfaces of theelectrical connectors 406, die connectors 488, insulating layer 490, andencapsulant 502 are level after the grinding process.

FIG. 27 illustrates further processing on the structure of FIG. 26. Theprocessing between these two figures is similar to the processingillustrated and described above in reference to FIGS. 10 and 11 withFIG. 11 being an equivalent intermediate stage as FIG. 27 and thedescriptions are not repeated herein. In FIG. 27, the redistributionstructure 410 is formed to be over and electrically coupled to thethrough vias 406 and die connectors 488.

FIG. 28 illustrates further processing on the structure of FIG. 27. Theprocessing between these two figures is similar to the processingillustrated and described above in reference to FIGS. 12 through 14 withFIG. 14 being an equivalent intermediate stage as FIG. 28 and thedescriptions are not repeated herein. In FIG. 28, a second package 450is bonded to package structure 500 of FIG. 27.

Further processing may be performed on the package structure of FIG. 28.For example, the package structure of FIG. 28 may be mounted to apackage substrate using the conductive connectors 416.

FIGS. 29 through 34 illustrate cross-sectional views of another packagestructure in accordance with some embodiments. The embodiment in FIGS.39 through 34 is similar to the embodiment illustrated in FIGS. 22through 28 except that this embodiment, the integrated circuit die 100does not include die connectors 488 and insulating layer 490 on the pads104 on the active side of the integrated circuit die 100. This removalof the die connectors 488 and insulating layer 490 requires an extracarrier substrate bonding/debonding to protect the pads 104. Detailsregarding this embodiment that are similar to those for the previouslydescribed embodiment will not be repeated herein.

FIG. 29 illustrates the integrated circuit die 100 bonded to theintegrate circuit die 200 as described above in FIG. 24 and thedescription is not repeated herein. The bonding was described in FIGS. 2and 3 above and the descriptions are not repeated herein. In FIG. 29,the integrated circuit dies 100 and 200 are bonded together with bondingjoints 300. The bonding joints 300 can be any of the bonding jointconfigurations 300A-300O in FIGS. 4A-4O.

FIG. 30 illustrates further processing on the structure of FIG. 29. Theprocessing between these two figures is similar to the processingillustrated and described above in reference to FIGS. 3 through 8 withFIG. 8 being an equivalent intermediate stage as FIG. 30 and thedescriptions are not repeated herein. The bonded integrated circuit dies100 and 200 are encapsulated with encapsulant 522 to form a package 524.

FIG. 30 further illustrates the attaching of the package 524 on acarrier substrate 400 similar to that described above in FIGS. 7 and 8and the descriptions are not repeated herein. In FIG. 30, the package524 is attached to the carrier with the integrated circuit die 100nearer to the carrier substrate 400 than the integrated circuit die 200.

FIG. 31 illustrates further processing on the structure of FIG. 30. Theprocessing between these two figures is similar to the processingillustrated and described above in reference to FIGS. 9 and 10 with FIG.10 being an equivalent intermediate stage as FIG. 31 and thedescriptions are not repeated herein. The package 524 is encapsulatedwith encapsulant 526 and the upper surface is planarized.

In FIG. 31, the encapsulant 526 can undergo a grinding process to exposethe electrical connectors 406. Surfaces of the electrical connectors 406and encapsulant 526 are level after the grinding process.

FIG. 32 illustrates further processing on the structure of FIG. 31. InFIG. 32, the carrier substrate 400 is debonded and the structure isflipped over and bonded to another carrier substrate 530. The debondingprocess was described above and the description is not repeated herein.In FIG. 32, the package 524 is attached to the carrier with theintegrated circuit die 200 nearer to the carrier substrate 530 than theintegrated circuit die 100. In FIG. 32, the exposed surface of theencapsulant 526, the electrical connectors 406 and the pads 104, andsemiconductor substrate 102, are level without the grinding process.

FIG. 33 illustrates further processing on the structure of FIG. 32. Theprocessing between these two figures is similar to the processingillustrated and described above in reference to FIGS. 10 and 11 withFIG. 11 being an equivalent intermediate stage as FIG. 33 and thedescriptions are not repeated herein. In FIG. 33, the redistributionstructure 410 and conductive connectors 416 are formed to be over andelectrically coupled to the through vias 406 and pads 104.

FIG. 34 illustrates further processing on the structure of FIG. 33. Theprocessing between these two figures is similar to the processingillustrated and described above in reference to FIGS. 12 through 14 withFIG. 14 being an equivalent intermediate stage as FIG. 34 and thedescriptions are not repeated herein. In FIG. 34, a second package 450is bonded to package structure 540 of FIG. 33.

Further processing may be performed on the package structure of FIG. 34.For example, the package structure of FIG. 34 may be mounted to apackage substrate using the conductive connectors 416.

FIGS. 35 through 38 illustrate cross-sectional views of another packagestructure in accordance with some embodiments. The embodiment in FIGS.35 through 38 is similar to the embodiment illustrated in FIGS. 1through 14 except that this embodiment, there is a gap between thedielectric layers of the integrated circuit dies 100 and 200 after theyare bonded. Details regarding this embodiment that are similar to thosefor the previously described embodiment will not be repeated herein.

FIG. 35 illustrates the integrated circuit die 100 bonded to theintegrate circuit die 200 as described in FIGS. 2 and 3 above and thedescriptions are not repeated herein. In FIG. 35, the integrated circuitdies 100 and 200 are bonded together with bonding joints 300. Thebonding joints 300 in this embodiment are the bonding jointconfiguration 300D in FIG. 4D. This embodiment includes the standoff gapbetween the dielectric layers of the integrated circuit dies 100 and200.

FIG. 36 illustrates further processing on the structure of FIG. 35. InFIG. 36, a sealing layer 546 is formed over the various components toseal the bonding interface between the integrated circuit dies 100 and200. The sealing of the bonding interface can help the reliability ofthis embodiment as compared to not sealing the bonding interface in thisconfiguration. The sealing layer 546 can be formed of similar materialsand processes as the insulating layer 208 described above and thedescription is not repeated herein. In accordance of a embodiment, thesealing layer can be formed of polymer materials, for example, aParylene, a polyimide, a BCB, and a PBO or the like. The forming methodsmay be by spraying, jetting, coating or the like.

FIG. 37 illustrates further processing on the structure of FIG. 36. Theprocessing between these two figures is similar to the processingillustrated and described above in reference to FIG. 5 with FIG. 5 beingan equivalent intermediate stage as FIG. 37 and the descriptions are notrepeated herein. The bonded integrated circuit dies 100 and 200 areencapsulated with encapsulant 548 to form a package.

FIG. 38 illustrates further processing on the structure of FIG. 37. Theprocessing between these two figures is similar to the processingillustrated and described above in reference to FIGS. 5 through 14 withFIG. 14 being an equivalent intermediate stage as FIG. 38 and thedescriptions are not repeated herein. In FIG. 38, a second package 450is bonded to package structure 562 that includes the bonded integratedcircuit dies of FIG. 37.

Further processing may be performed on the package structure of FIG. 38.For example, the package structure of FIG. 38 may be mounted to apackage substrate using the conductive connectors 416.

By forming a PoP structure including dies bonded together with a hybridbonding technique utilizing solder instead of the typicalcopper-to-copper bonding of hybrid bonding. The bonding temperature ofthe hybrid bonding can be lowered significantly. In addition, the bondpads of the structures can be recessed to reduce the height of thepackage structure. The dies can be bonded together face-to-face (F2F) orface-to-back (F2B). For example, in a F2F bonding configuration theactive surfaces (faces) of the dies are bonded together, whereas in aF2B bonding configuration, an active surface of one die is bonded to aback surface of another die.

In an embodiment, a package includes a first package structure includinga first die having a first active side and a first back-side, the firstactive side including a first bond pad and a first insulating layer asecond die bonded to the first die, the second die having a secondactive side and a second back-side, the second active side including asecond bond pad and a second insulating layer, the second active side ofthe second die facing the first active side of the first die, the secondinsulating layer being bonded to the first insulating layer throughdielectric-to-dielectric bonds, and a conductive bonding material bondedto the first bond pad and the second bond pad, the conductive bondingmaterial having a reflow temperature lower than reflow temperatures ofthe first and second bond pads.

Embodiments may include one or more of the following features. Thepackage where the first insulating layer is bonded to the secondinsulating layer with respective bonds including O—H bonds. The packagewhere the first bond pad is recessed into the first insulating layer.The package where the first insulating layer and the second insulatinglayer are both made of a polymer. The package where the first insulatinglayer and the second insulating layer are both made of silicon nitride,silicon oxide, phosphosilicate glass (PSG), borosilicate glass (BSG),boron-doped phosphosilicate glass (BPSG), or a combination thereof. Thepackage where there is void surrounding the conductive bonding materialand between the first and second bond pads. The package where the firstpackage structure further includes a conductive pad on the first activeside of the first die, a first through via electrically coupled to theconductive pad, a first encapsulant on the first die and laterallyencapsulating the second die and the first through via, the firstthrough via extending through the first encapsulant; and a firstredistribution structure over the second die, the first through via, andthe first encapsulant, the first redistribution structure beingelectrically coupled to the first through via. The package where thefirst package structure further includes a second through via adjacentthe first die, and a second encapsulant encapsulating the first die, thefirst encapsulant, and the second through via, the second through viaextending through the second encapsulant, the first redistributionstructure being electrically coupled to the second through via. Thepackage further including a second package structure bonded to thesecond through via by a first conductive connector.

In an embodiment, a method including forming a first package includingbonding a first side of a first die to a second side of a second diewith a conductive bonding material and a first and second insulatinglayers, the first side including a first bond pad and the firstinsulating layer, the second side including a second bond pad and thesecond insulating layer, the second side of the second die facing thefirst side of the first die, the second insulating layer being bonded tothe first insulating layer through dielectric-to-dielectric bonds, theconductive bonding material bonded to the first bond pad and the secondbond pad, the conductive bonding material having a reflow temperaturelower than reflow temperatures of the first and second bond pads.

Embodiments may include one or more of the following features. Themethod where forming the first package further includes forming a firstconductive pillar on and electrically coupled to a third bond pad on thefirst side of the first die, and encapsulating the first die, the seconddie, and the first conductive pillar with a first encapsulant. Themethod where forming the first package further includes forming anelectrical connector over a carrier substrate attaching the bonded firstand second dies to the carrier substrate adjacent the electricalconnector, the first die being adjacent the carrier substrate,encapsulating the bonded first and second dies, the first encapsulant,and the electrical connector with a second encapsulant, and forming afirst redistribution structure over the first die, the second die, thefirst encapsulant, the second encapsulant, and the electrical connector,the first redistribution structure being electrically coupled to thefirst conductive pillar and the electrical connector. The method furtherincluding removing the carrier substrate, and bonding a second packageto the electrical connector of the first package using a firstconductive connector, the second package being proximate the first die.The method where forming the first package further includes forming avia in the first die, encapsulating the first die and the second diewith a first encapsulant, forming an electrical connector over a carriersubstrate, attaching the encapsulant and bonded first and second dies tothe carrier substrate adjacent the electrical connector, the second diebeing adjacent the carrier substrate, encapsulating the bonded first andsecond dies, the first encapsulant, and the electrical connector with asecond encapsulant, planarizing the encapsulant, where after planarizingthe electrical connector and the via in the first die are exposed,forming a first redistribution structure over the first die, the seconddie, the first encapsulant, the second encapsulant, and the electricalconnector, the first redistribution structure being electrically coupledto the via in the first die and the electrical connector, and formingconductive connectors over and electrically coupled to the firstredistribution structure. The method where the first insulating layerand the second insulating layer are both made of a polymer. The methodwhere the first insulating layer and the second insulating layer areboth made of silicon nitride, silicon oxide, phosphosilicate glass(PSG), borosilicate glass (BSG), boron-doped phosphosilicate glass(BPSG), or a combination thereof.

In an embodiment, a method includes forming a first insulating layerover a first side of a first wafer, patterning a recess in the firstinsulating layer, conformally depositing a conductive material in therecess and over the first insulating layer, a thickness of theconductive material being less than a thickness of the first insulatinglayer, removing portions of the conductive material outside of therecess to form a first bond pad, the first bond pad and the firstinsulating layer being on a first active side of a first die in thefirst wafer, forming a second die including a second active side, thesecond active side including a second bond pad and a second insulatinglayer, forming a conductive bump on the second bond pad, the conductivebump having a reflow temperature lower than reflow temperatures of thefirst and second bond pads, bonding the conductive bump on the secondbond pad to the first bond pad; and bonding the second insulating layerof the second die to the first insulating layer.

Embodiments may include one or more of the following features. Themethod further including forming a first conductive pillar on andelectrically coupled to a third bond pad on the first active side of thefirst die; encapsulating the first wafer, the second die, and the firstconductive pillar with a first encapsulant, and singulating the firstwafer and the first encapsulant, the singulating forming a first packagestructure including the first die, the second die, the first conductivepillar, and the first encapsulant. The method further including formingan electrical connector over a carrier substrate, attaching the firstpackage structure to the carrier substrate adjacent the electricalconnector, the first die being adjacent the carrier substrate;encapsulating the first package structure and the electrical connectorwith a second encapsulant; and forming a first redistribution structureover the first package structure, the second encapsulant, and theelectrical connector, the first redistribution structure beingelectrically coupled to the first conductive pillar and the electricalconnector.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A device comprising: a first integrated circuitdie comprising a first conductive feature, a first insulating layeraround the first conductive feature, and a bond pad on the firstconductive feature and the first insulating layer; a second integratedcircuit die comprising a second conductive feature and a secondinsulating layer around the second conductive feature; and a conductivebonding layer connecting the bond pad to the second conductive feature,a reflow temperature of the conductive bonding layer being lower than areflow temperature of the bond pad, wherein the second insulating layeris physically separated from the bond pad by a void, sidewalls of theconductive bonding layer and a top surface of the bond pad being exposedto the void.
 2. The device of claim 1 further comprising: a barrierlayer disposed between the second conductive feature and the conductivebonding layer, sidewalls of the barrier layer being exposed to the void.3. The device of claim 2 further comprising: a first polymer layer onthe first insulating layer, the first polymer layer being disposedaround the bond pad and the conductive bonding layer; and a secondpolymer layer on the second insulating layer, the second polymer layerbeing disposed around the barrier layer and the conductive bondinglayer, wherein the first polymer layer and the second polymer layer aredirectly bonded by polymer bonding.
 4. The device of claim 3, whereinsidewalls of the first polymer layer and the second polymer layer areexposed to the void.
 5. The device of claim 1, wherein the bond padcomprises: a seed layer on the first conductive feature and the firstinsulating layer; a barrier layer on the seed layer; and a conductivematerial layer on the barrier layer.
 6. The device of claim 5, whereinsidewalls of the seed layer, the barrier layer, and the conductivematerial layer are exposed to the void.
 7. A device comprising: a firstintegrated circuit die comprising a first conductive feature and a firstinsulating layer around the first conductive feature; a secondintegrated circuit die comprising a second conductive feature and asecond insulating layer around the second conductive feature, the secondinsulating layer having a major surface facing the first integratedcircuit die; and a conductive bonding layer connecting the firstconductive feature to the second conductive feature, the conductivebonding layer extending partially into the first conductive feature, areflow temperature of the conductive bonding layer being lower than areflow temperature of the first conductive feature, wherein the firstinsulating layer is physically separated from the second insulatinglayer by a void, and wherein the major surface of the second insulatinglayer and sidewalls of the conductive bonding layer are exposed to thevoid.
 8. The device of claim 7, wherein a width of the first conductivefeature is less than a width of the void.
 9. The device of claim 7,wherein a width of the first conductive feature is greater than a widthof the void.
 10. The device of claim 7, wherein the first integratedcircuit die further comprises a semiconductor substrate, the firstinsulating layer being disposed on the semiconductor substrate, andwherein the first conductive feature comprises: a via extending throughthe first insulating layer and at least a portion of the semiconductorsubstrate.
 11. The device of claim 7, wherein the first integratedcircuit die further comprises a semiconductor substrate, the firstinsulating layer being disposed on the semiconductor substrate, andwherein the first conductive feature comprises: a pad on thesemiconductor substrate; and a first via extending through at least aportion of the semiconductor substrate, the via being connected to thepad.
 12. The device of claim 11, wherein the first via is one of aplurality of vias extending through at least a portion of thesemiconductor substrate, each one of the vias being connected to thepad.
 13. The device of claim 11 further comprising: a third insulatinglayer disposed between the first insulating layer and the secondinsulating layer, the third insulating layer being disposed around theconductive bonding layer.
 14. The device of claim 13 further comprising:a barrier layer disposed between the second conductive feature and theconductive bonding layer, sidewalls of the barrier layer being exposedto the void, the third insulating layer being disposed around thebarrier layer.
 15. A device comprising: a first integrated circuit diecomprising a first insulating layer and a first conductive featureextending through the first insulating layer, the first conductivefeature having a first portion and a second portion disposed around thefirst portion, the first portion having a first thickness, the secondportion having a second thickness, the second thickness being greaterthan the first thickness; a second integrated circuit die comprising asecond conductive feature and a second insulating layer around thesecond conductive feature; and a conductive bonding layer connecting thefirst conductive feature and the second conductive feature, theconductive bonding layer being a different conductive material than thefirst conductive feature, sidewalls of the conductive bonding layerbeing physically separated from sidewalls of the second portion of thefirst conductive feature by a void.
 16. The device of claim 15, whereinthe first insulating layer is bonded to the second insulating layer. 17.The device of claim 15, wherein the first insulating layer is physicallyseparated from the second insulating layer by the void.
 18. The deviceof claim 15 further comprising: a first polymer layer on the firstinsulating layer; and a second polymer layer on the second insulatinglayer, wherein the first polymer layer and the second polymer layer aredirectly bonded by polymer bonding.
 19. The device of claim 15, whereinthe conductive bonding layer has a first portion proximate the firstconductive feature and a second portion proximate the second conductivefeature, a width of the first portion being greater than a width of thesecond portion.
 20. The device of claim 15, wherein a height of thesecond portion of the first conductive feature is equal to a combinedheight of the void and the first portion of the first conductivefeature.